1. Field of the Invention
This invention relates to a process for the separation and subsequent recovery of particulate matter from solution. More particularly, this invention relates to a process for the separation and recovery of particulate matter having an average diameter of about 1 micron or less through the use of bi-phase systems and the modification of the surface properties of said particulate matter to selectively modify its migration to one of the phases of said bi-phase system.
2. Prior Art
The technology relating to the separation and recovery of particulate matter from solution has received increasing attention. This is in part due to the abundance of industrially-produced material and the increased concern regarding its proper disposal.
Numerous technical solutions have been proposed for the concentration and disposal of particulate matter from the various types of waste slimes. The simplest of these techniques involve sedimentation of the particular matter. However, as these methods rely simply upon specific gravity, their utility is limited to the separation of relatively large particles, i.e. larger than about 50 microns.
Filtration technology has also been widely employed. However, these methods have proved to be relatively capital-intensive. Furthermore, small pore filters are typically fragile, unable to handle great volumes of solutions and are more suspectible to clogging. They are therefore not highly useful in the treatment of typical industrial waste streams.
Froth floatation techniques have therefore been developed in an effort to effect satisfactory separations of particulate matter less than 50 microns in diameter. Basically, these techniques involve the addition of reagents, such as surfactants, to the solution in which the particulate matter is contained and the injection of air through the base of a solution containing vessel, thereby causing a frothing of the solution. The particulate matter, bound to air bubbles, rises from solution and may be removed from the vessel along with the froth. Early examples of this technology are disclosed in U.S. Pat. Nos. 835,120 and 962,678.
However, while these techniques have greatly evolved, they continue to possess limitations when dealing with particles of less than about 10 microns in diameter. These limitations are, to varying degrees, associated with at least one of the following phenomena.
A. Fine particles possess large surface areas and therefore processes for their concentration consume large quantities of floatation reagents.
B. Fine particles of one material often agglomerate with larger particles, thereby inhibiting the separation of said fine particles.
C. Floatation rate varies directly with particle size, thereby limiting application of this technology to particles having diameters greater than about 10 microns.
In order to achieve recoveries of particles having smaller diameters, various floation-related techniques have been developed including oil agglomeration and oil floatation. These processes, while allowing recoveries of smaller particles, suffer their own drawbacks due to the relatively high cost of the petroleum-based reagents employed therein and the environmental concerns associated therewith.
A solution to this problem has been proposed in Dutch Patent Application No. 83-03971, published June 17, 1985. The process disclosed therein involves the separation of metal minerals and gangue using a bi-phase aqueous system of an aqueous metal sulfate solution and an aqueous solutions of a polyethylene glycol. It is reported that the lighter gangue particles collect in the upper, polyethylene glycol-containing phase while the metal minerals remain in the metal sulfate solution. While the process effectively solves the environmental concerns due to the absence of toxic, petroleum reagents, the process does not offer selective control of the partition of these materials.
In view of the inadequacies associated with the above-mentioned techniques, there is a need for a method allowing for the separation of particulate matter which does not depend solely upon density considerations, does not employ toxic petroleum-based materials and offers selective modification of the partition of particulate matter.
It is therefore an object of the instant invention to provide a process for the separation of particulate matter which is not density dependent.
It is a further object of the instant invention to provide a process for the separation of particulate matter which does not employ toxic petroleum-based materials.
It is still a further object of the instant invention to provide a process for the separation of particulate matter having diameters of 1 micron or less.